<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<style>
		.a {
			width: 100px;
			height:100px;
			border: red solid 1px;
		}
		.a:hover {
			background-color: green;
		}
	</style>
	<div class="a">
	</div>
	<body>
	</body>
</html>